1. Field of the Invention
The present invention relates generally to a communication apparatus, and more particularly to a housing structure for an ultrafast communication apparatus.
2. Description of the Related Art
A communication apparatus such as a transmission device and a switching device is configured by vertically mounting a plurality of plug-in units (PIU) to a back wiring board mounted in a shelf. Each plug-in unit is provided by an electronic circuit package. That is, each plug-in unit includes a printed wiring board and a plurality of electronic components such as LSIs having electronic circuits mounted on the printed wiring board. By vertically mounting the package type plug-in units to the back wiring board mounted in the shelf as mentioned above, the communication apparatus can be simplified and economized in design, and can be improved in maintainability.
In high-speed transmission, it is necessary to ensure a capability of resisting EMI. As conventional countermeasures against EMI, each plug-in unit is constructed of a box-shaped structure to thereby realize an electromagnetically sealed structure. However, such countermeasures against EMI have disadvantages that the structure of each plug-in unit is complicated and that a cost increase is invited. Further, also in a communication apparatus having a shielding structure using a gasket, all opening portions of the communication apparatus are not managed by a cutoff frequency, and it is hard to cope with high-frequency EMI at present. In this shielding structure such that the plug-in units adjacent to each other are in close contact with each other through the gasket, the gasket exerts an elastic force in the lateral direction of each plug-in unit, causing a hindrance to smooth insertion/ejection of each plug-in unit with respect to the shelf.
Further, such a conventional communication apparatus employs a punching metal as a shield board for ensuring EMI resistance and fire resistance. The punching metal has a low opening ratio, so that the air-flow resistance of cooling air for the communication apparatus is high, causing a bottleneck in improving the cooling performance. Moreover, the thickness of the punching metal must be increased to satisfy the cutoff frequency, causing an increase in weight. Further, it is necessary to ensure the reliability of connection between each plug-in unit and the back wiring board in applying connectors for ultrafast transmission. A conventional lever for use in plug-in connection of the connectors of each plug-in unit and the back wiring board is limited in its engagement accuracy. In particular, a connector with a short engagement length under development for ultrahigh frequencies cannot ensure a sufficient connection reliability. Accordingly, any additional fixing means such as a screw must be provided to sufficiently engage the connectors by the use of the conventional lever.
It is apparent that the traffic and transmission speed in the future communication field will be increased. In relation thereto, the housing structure of the conventional communication apparatus is unsatisfactory in the following points.
(1) EMI resistance in ultrafast transmission
(2) Reliability of connection between each plug-in unit and the back wiring board in applying the connectors for ultrafast transmission
(3) Cooling performance for suppression of heating due to an increase in power consumption
(4) Fire resistance
(5) High-density mount capable of supporting an increase in number of cable interfaces
Accordingly, for realization of ultrafast transmission, it is necessary to ensure sufficient EMI resistance and fire resistance, to improve the cooling performance, and to mount heating components at a high density. Thus, these theoretically conflicting conditions must be satisfied.
It is therefore an object of the present invention to provide a communication apparatus which can ensure sufficient EMI resistance and cooling performance and can mount heating components at a high density.
In accordance with an aspect of the present invention, there is provided a communication apparatus increasing a shelf formed of metal, the shelf having a pair of side plates; a back wiring board mounted in the shelf on the back side thereof, the back wiring board having a plurality of first connectors and a solid ground pattern; an upper guide plate mounted in the shelf on the upper side thereof, the upper guide plate having a plurality of guide rails and a plurality of vent holes; a first shield board mounted on the upper guide plate, the first shield board having numerous openings; a lower guide plate mounted in the shelf on the lower side thereof, the lower guide plate having a plurality of guide rails and a plurality of vent holes; a second shield board mounted on the lower guide plate, the second shield board having numerous openings; a plurality of plug-in units mounted in the shelf so as to be inserted along the guide rails of the upper guide plate and the guide rails of the lower guide plate, each of the plug-in units having a printed wiring board, a second connector mounted on the printed wiring board and connected to one of the first connectors, a front structure fixed to the front end of the printed wiring board, the front structure having an upper surface, a pair of side surfaces, and a lower surface, and a first conductive gasket continuously mounted on the upper surface, one of the side surfaces, and the lower surface of the front structure; and a second conductive gasket mounted on one of the side plates of the shelf; the second conductive gasket being in close contact with the front structure of one of the plug-in units adjacent to the one side plate of the shelf, the first conductive gasket of the one plug-in unit being in close contact with the front structure of another one of the plug-in units adjacent to the one plug-in unit or in close contact with the other side plate of the shelf, thereby realizing electromagnetic shield on the front side of the shelf; the first shield board realizing electromagnetic shield on the upper side of the shelf; the second shield board realizing electromagnetic shield on the lower side of the shelf; the ground pattern of the back wiring board realizing electromagnetic shield on the back side of the shelf; the side plates of the shelf realizing electromagnetic shield on the right and left sides of the shelf.
The communication apparatus further includes an external cable inserted in the front structure of each plug-in unit; the front structure of each plug-in unit having a shielded external cable introducing portion for introducing the external cable to the printed wiring board. The communication apparatus further increases an upper strike plate mounted on the front side of the upper guide plate; and a lower strike plate mounted on the front side of the lower guide plate.
Preferably, the upper surface of the front structure of each plug-in unit has a first projection; the lower surface of the front structure of each plug-in unit has a second projection; the upper strike plate has a plurality of recesses for respectively engaging the first projections of the plug-in units; and the lower strike plate has a plurality of recesses for respectively engaging the second projections of the plug-in units. Preferably, the recesses of the upper strike plate increase a plurality of guide rails respectively aligned with the guide rails of the upper guide plate; and said recesses of the lower strike plate increase a plurality of guide rails respectively aligned with the guide rails of the lower guide plate. Alternatively, the upper surface of the front structure of each plug-in unit may have a first recess; the lower surface of the front structure of each plug-in unit may have a second recess; the upper strike plate may have a plurality of projections for respectively engaging the first recesses of the plug-in units; and the lower strike plate may have a plurality of projections for respectively engaging the second recesses of the plug-in units.
With this configuration, the plug-in units vertically mounted in the shelf are fixed by the engagement of the first connectors of the back wiring board and the second connectors of the plug-in units on the back side of the shelf and by the engagement of the projections or recesses of the plug-in units and the recesses or projections of the upper and lower strike plates on the front side of the shelf. Accordingly, although the gaskets of the adjacent plug-in units exert elastic forces in the lateral direction, the elastic forces can be absorbed to some extent by the engagement of the projections and the recesses on the front side of the shelf, so that the insertion/ejection of the plug-in units are not hindered by the elastic forces.
Preferably, each of the first and second shield boards increases a honeycomb shield board having numerous honeycomb-shaped openings. Preferably, the front structure of each plug-in unit has a pair of upper and lower levers pivotably mounted at upper and lower end portions, each of the levers having a first engaging portion and a second engaging portion; the upper strike plate having a groove for engaging the first engaging portion of the upper lever; the lower strike plate having a groove for engaging the first engaging portion of the lower lever.
Preferably, the upper guide plate has a plurality of first elastic lock members respectively corresponding to the plug-in units and biased downward; the lower guide plate has a plurality of second elastic lock members respectively corresponding to the plug-in units and biased upward; and the printed wiring board of each plug-in unit has a first notch for engaging the corresponding first elastic lock member and a second notch for engaging the corresponding second elastic lock member. Preferably, the front structure of each plug-in unit has a first unlocking mechanism for disengaging the corresponding first elastic lock member from the first notch, and a second unlocking mechanism for disengaging the corresponding second elastic lock member from the second notch.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.